Effect of rearing temperature on sex ratio in juvenile Atlantic halibut, Hippoglossus hippoglossus

Several flatfish species exhibit temperature-dependent sex determination. This research investigated the effects of rearing temperature on sex ratio in Atlantic halibut, Hippoglossus hippoglossus, a species in which females grow larger and faster than males under culture conditions. Previous research has shown that ovarian differentiation occurs in Atlantic halibut in the size interval of 38–50 mm, and precedes the differentiation of testes. In the current study, triplicate groups of juvenile Atlantic halibut were reared at each of three temperatures (7, 12 and 15°C) from an initial mean size of 21 mm to a final mean size of 80 mm (total length). The sex of each fish was then determined by macroscopic and histological examination of the gonads. Sex ratios were not significantly different from 1:1 in any group, suggesting that sex in this species is not influenced by temperature.